1. Field of the Invention
This invention relates generally to antennas and more particularly to an antenna which is combined with and a part of a radome structure used on an aircraft, projectile, guided missile, or the like.
2. Technical Considerations and Prior Art
Airborne or vehicle-carried radar equipment is almost always covered by a plastic or dielectric radome which is substantially transparent to electromagnetic energy but which provides mechanical protection for the equipment and contributes to the streamlining of the vehicle. Situated within the radome itself is the antenna system of the radar equipment. Typically, the antenna system is servo-actuated to provide mechanical scanning. Although such structures have served their purposes satisfactorily in the past, they have become less satisfactory with the increased complexities and sophistication of today's modern radar equipment. There has been a pressing need for a reduction in both bulk and cost of radar equipment to make modern equipment competitive with less accurate equipment in many applications. It is necessary that this be accomplished without sacrificing electrical performance. With the advent of simple and compact phase shifting devices, electrical scanning of radar antennas has become practical, and servo-actuated antenna arrays have been replaced with fixed positioned arrays. There has thus resulted some decrease in size, weight and expense in radar equipment; however, these improvements, while abating the problem, have not eliminated it.
In many cases, the fixed antenna systems are designed independently of the radome and radiate through the radome into free space. While this approach is widely accepted, there are still many problems, because since the radome and antenna are separate components, there is antenna-radome interference caused by air gaps, improper bonding, etc., which distorts the radiation pattern. Furthermore, scattered radio frequency energy is difficult to control with this arrangement, and frequently finds its way into the electronic system controlling the antenna and the vehicle. The cost of designing and constructing separate components and then matching the components together is quite high, since such design and construction must eliminate or at least minimize the afore-mentioned problems.
Various attempts have been made to mount the antenna flush with the skin of the carrying vehicle in order to obviate these problems. A successful approach is disclosed in U.S. Pat. No. 3,346,865, issued to one of the inventors of the instant invention. However, this approach does not provide the flexibility which is sometimes desired in missile design. Generally, the antenna disclosed in U.S. Pat. No. 3,346,865 is limited to high-frequency operation and does not readily adapt to multifunctional approaches, wherein different frequencies, multiphased and multidirectional operation would be advantageous. In view of these considerations, a more flexible approach is required.